Automatic adjustment of the water level in the tank. Level sensor assembly kit

21.02.2021

Often it is not enough to have only a pump for pumping out or replenishing water, it is also necessary to control it, that is, to turn it on and on on time. Everything would be fine if such processes are planned for you, and if not, then what to do? Let's say you have a cellar where water comes in ... Or the opposite situation. There is a tank that must always be full, ready for watering. During the day, the water gets warm, and in the evening you water. So, one and the other must be constantly monitored, and this is all the time, worries, your labors. But in our century, such tasks are already being solved once or twice, that is, the process can be automated. As a result, the automation will do everything for you, pump or pump out water, and you just have to very rarely monitor it. Check its performance. Well, my article will just be devoted to such a topic as the implementation of a scheme for pumping or pumping water by level, then I will tell you about this in more detail and in detail.

Control circuit (shutdown) of the pump for pumping water by level

I'll start with the scheme for pumping water, that is, when you are faced with the task of pumping water to a certain level, and then turning off the pump so that it does not idle. Take a look at the diagram below.

It is such a basic electrical circuit that is capable of pumping out water to a predetermined level. Let's take a look at how it works, what's here and why.

So, let's imagine that water replenishes our reservoir, it doesn't matter if it is your room, cellar or tank ... As a result, when the water reaches the upper reed switch SV1, voltage is applied to the P1 control relay coil. Its contacts are closed, and through them there is a parallel connection to the reed switch. Thus, the relay is self-locking. The power relay P2 also turns on, which switches the pump contacts, that is, the pump turns on for pumping. Further, the water level begins to decrease and reaches the SV2 reed switch, in this case it closes and supplies a positive potential to the coil winding. As a result, there is a positive potential on the coil on both sides, the current does not flow, the magnetic field of the relay weakens - relay P1 turns off. When P1 is turned off, the power supply for the P2 relay is also turned off, that is, the pump also stops pumping water. Depending on the power of the pump, you can choose a relay for the current you need.
I didn't say anything about the 200 ohm resistor. It is necessary so that in the process of switching on the SV2 reed switch, a short circuit with a minus does not occur through the relay contacts. It is best to choose a resistor such that it allows relay P1 to operate reliably, but at the same time has the highest possible potential. In my case, it was 200 ohms. Another feature of the circuit is the use of reed switches. Their plus is obvious when applied, they do not come into contact with water, which means that the electrical circuit will not be affected by possible changes in currents and potentials in various life situations, be it salty or dirty water ... The circuit will always work stably and "without misfires." There is no need to configure the circuit, everything works right away, with the correct connection.

After 2 months ...

Now about what was done a couple of months later, based on the requirements to reduce power consumption in standby mode. That is, this is the second version of everything that I described above.
You yourself understand that according to the diagram above, a 12 volt power supply will be constantly turned on, which, by the way, also consumes not free electricity! And based on this, it was decided to make a circuit for activating the pump for pumping out or filling water with a standby current of 0 mA. In fact, it turned out to be easy to implement. Take a look at the diagram below.

Initially, all circuits in the circuit are open, which means it consumes our stated 0 mA, that is, nothing. When the upper reed switch closes, the voltage across the transformer and the diode bridge turns on relay P1. Thus, the relay commutes through its contacts and a 36 Ohm resistor the power supply to the power supply unit and again to itself, that is, it self-picks up. The pump starts up. Further, when the water level reaches the bottom and the P2 relay is triggered, it breaks the self-pickup circuit of the P1 relay itself, thus de-energizing the entire circuit and putting it into standby mode. The 36 Ohm resistor serves to limit the current to the pump, at least slightly, when the upper reed switch is turned on. Thus, reducing the induction current on the reed switch and extending its life. When the power supply is already powered through relay P1, after it is triggered, then such a resistance will without problems provide voltage for holding the relay, that is, it will not be critical, and secondly, it will not warm up, since a small current will flow through it. This is just the current from losses in the winding and the current supplied to the relay P1. Therefore, the requirements for the resistor are not critical, unless you take it more powerful!
It remains to say that in any of these circuits, not only a reed switch, but also just end sensors can be used.

Well, now let's analyze the opposite situation, when it is necessary, on the contrary, to pump water into the tank and turn it off at a high level in it. That is, the pump turns on when the water level is low, and turns off when the water level is high.

"+" - ease of assembly and does not require adjustment. Does not consume current in standby mode!
"-" - The system has an end sensor operating with high voltage, so it is better to take it out of the water

Control circuit (shutdown) of the pump for filling water by level

If you cover our entire article briefly and at once with your glance, you will notice that we simply did not give the second scheme in the article, except for the one above.

In fact, this is a self-evident fact, because what is essentially the difference between the pumping circuit and the pumping circuit, except that the reed switches are located one below the second at the bottom. That is, if you rearrange the reed switches, or reconnect the contacts to them, then one circuit will turn into another.

I summarize that in order to convert the above circuit into a circuit for pumping water, swap the reed switches. As a result, the pump will turn on from the lower sensor - reed switch SV1, and disconnect at the upper level from the reed switch SV2.

Implementation of the installation of reed switches as end sensors for pump actuation depending on the water level

In addition to the electrical circuit, you will need to make a structure that ensures the closure of the reed switches, depending on the water level. For my part, I can offer you a couple of options that will satisfy such conditions. Take a look at them below.

In the first case, a construction is realized using a thread, a cable. In the second, a rigid structure, when the magnets are mounted on a rod floating on a float. There is no special sense in describing the elements of each of the structures, here, in principle, everything is perfectly clear.

Pump connection according to the operation scheme depending on the water level in the tank - summing up

The most important thing is that this circuit is very simple, does not require adjustment, and almost anyone can repeat it, even without experience with electronics. Second, the circuit is very reliable and consumes minimal power in standby mode (option 1) or nothing at all (option 2), since all its circuits are open. This means that consumption will be limited only by current losses in the power supply (option 1) or even less!

Video about the operation of level sensors for pumping and pumping water

Water supply and drainage is an integral part of everyday life and production. Almost everyone who was engaged in farming or home improvement has at least once faced the problem of maintaining the water level in a particular container. Some do it manually, opening and closing valves, but it is much easier and more efficient to use an automatic water level sensor for this purpose.

Level sensor types

Depending on the tasks set, contact and non-contact sensors are used to control the liquid level. The former, as you might guess from their name, have contact with the liquid, the latter receive information remotely using indirect measurement methods - the transparency of the medium, its capacity, electrical conductivity, density, etc. According to the principle of operation, all sensors can be divided into 5 main types:

Float.
Electrode.
Hydrostatic.
Capacitive.
Radar.

The first three can be attributed to devices of the contact type, since they directly interact with the working medium (liquid), the fourth and fifth are non-contact.

Float sensors

Perhaps the simplest in design. They are a float system that is located on the surface of the liquid. As the level changes, the float moves, in one way or another closing the contacts of the control mechanism. The more contacts are along the path of the float, the more accurate the indicator readings:

The principle of operation of the float water level sensor in the tank

The figure shows that the indicator readings of such a device are discrete, and the number of level values \u200b\u200bdepends on the number of switches. In the above diagram, there are two of them - upper and lower. This is usually sufficient to automatically maintain the level within the specified range.

There are float devices for continuous remote monitoring. In them, the float controls the rheostat engine, and the level is calculated based on the current resistance. Until recently, such devices were widely used, for example, to measure the amount of gasoline in the fuel tanks of cars:

Rheostat level gauge device, where:

1 - wire rheostat;
2 - rheostat slider mechanically connected to the float.

Electrode level sensors

Devices of this type use the electrical conductivity of a liquid and are discrete. The sensor consists of several electrodes of different lengths immersed in water. Depending on the level in the liquid, there is a certain number of electrodes.

Three-electrode system of liquid level sensors in the tank

In the picture above, the two right-hand sensors are immersed in water, which means there is water resistance between them - the pump is stopped. As soon as the level drops, the middle sensor will be dry, and the resistance of the circuit will increase. The automatics will start the booster pump. When the container is full, the shortest electrode will fall into the water, its resistance relative to the common electrode will decrease and the automation will stop the pump.

It is quite clear that the number of control points can be easily increased by adding additional electrodes and appropriate control channels to the design, for example, for overflow or dry out alarms.

Hydrostatic control system

Here the sensor is an open tube in which a pressure sensor of one type or another is installed. As the level increases, the height of the water column in the tube changes, and hence the pressure on the sensor:

How the Hydrostatic Liquid Level Control System Works

Such systems have a continuous characteristic and can be used not only for automatic control, but also for remote level control.

Capacitive measurement method

The principle of operation of a capacitive sensor with a metal (left) and dielectric bath

Induction pointers work according to a similar principle, but in them the role of a sensor is played by a coil, the inductance of which changes depending on the presence of liquid. The main disadvantage of such devices is that they are suitable only for monitoring substances (liquids, bulk materials, etc.) that have a sufficiently high magnetic permeability. In everyday life, inductive sensors are practically not used.

Radar control

The main advantage of this method is the lack of contact with the work environment. Moreover, the sensors can be far enough away from the liquid, the level of which must be controlled, - meters. This allows radar sensors to be used to monitor extremely corrosive, toxic or hot liquids. The principle of operation of such sensors is indicated by their very name - radar. The device consists of a transmitter and a receiver, assembled in one housing. The first one emits one or another type of signal, the other receives the reflected one and calculates the delay time between the sent and received pulses.

Working Principle of Ultrasonic Radar Type Level Switch

The signal, depending on the assigned tasks, can be light, sound, radio emission. The accuracy of such sensors is quite high - millimeters. Perhaps the only drawback is the complexity of the radar monitoring equipment and its rather high cost.

Homemade liquid level regulators

Due to the fact that some of the sensors are extremely simple in design, it is not difficult to create a water level switch with your own hands... Working in conjunction with water pumps, such devices will fully automate the process of pumping water, for example, to a country water tower or an autonomous drip irrigation system.

Automatic float pump control

To implement this idea, a homemade reed switch water level sensor with a float is used. It does not require expensive and scarce components, is easy to repeat and reliable enough. First of all, it is worth considering the design of the sensor itself:

Design of a two-level float water sensor in a tank

It consists of the actual float 2, which is fixed on the movable rod 3. The float is located on the surface of the water and, depending on its level, moves together with the rod and the permanent magnet 5 fixed on it up / down in guides 4 and 5. In the lower position, when the liquid level is minimal, the magnet closes reed switch 8, and in the upper one (the tank is full) - reed switch 7. The length of the stem and the distance between the guides are selected based on the height of the water tank.

It remains to assemble a device that will automatically turn on and off the booster pump, depending on the state of the contacts. Its scheme looks like this:

Water pump control circuit

Suppose the tank is completely full and the float is in the up position. Reed switch SF2 is closed, transistor VT1 is closed, relays K1 and K2 are disabled. The water pump connected to the XS1 connector is de-energized. As the water flows, the float, and with it the magnet, will go down, the SF1 reed switch will open, but the circuit will remain in the same state.

As soon as the water level falls below the critical level, the SF1 reed switch closes. Transistor VT1 will open, relay K1 will work and stand on self-locking with contacts K1.1. At the same time, the contacts K1.2 of the same relay will supply power to the K2 starter, which turns on the pump. Water pumping began.

As the level increases, the float will begin to rise, contact SF1 will open, but the transistor blocked by contacts K1.1 will remain open. As soon as the container is full, the SF2 contact closes and forcibly closes the transistor. Both relays will release, the pump will shut down and the circuit will go into standby mode.

When repeating the circuit in place of K1, you can use any low-power electromagnetic relay for an actuation voltage of 22-24 V, for example, RES-9 (RS4.524.200). As K2, RMU (RS4.523.330) or any other for a response voltage of 24 V is suitable, the contacts of which can withstand the inrush current of the water pump. Any reed switches will work for closing or switching.

Level switch with electrode sensors

With all its advantages and simplicity, the previous design of the level gauge for tanks has a significant drawback - mechanical assemblies operating in water and requiring constant maintenance. This disadvantage is absent in the electrode design of the machine. It is much more reliable than mechanical, does not require any maintenance, and the circuit is not much more complicated than the previous one.

Here, three electrodes made of any conductive stainless material are used as sensors. All electrodes are electrically isolated from each other and from the vessel body. The design of the sensor is clearly visible in the figure below:

The design of a three-electrode sensor, where:

S1 - common electrode (always in water)
S2 - minimum sensor (tank is empty);
S3 - maximum level sensor (tank full);

The pump control scheme will look like this:

Scheme of automatic pump control using electrode sensors

If the tank is full, then all three electrodes are in water and the electrical resistance between them is low. In this case, the transistor VT1 is closed, VT2 is open. Relay K1 is on and with its normally closed contacts de-energizes the pump, and with its normally open contacts connects the S2 sensor in parallel with S3. When the water level starts to drop, electrode S3 is exposed, but S2 is still in the water and nothing happens.

Water continues to be consumed and finally the S2 electrode is exposed. Thanks to the resistor R1, the transistors go to the opposite state. The relay releases and starts the pump while simultaneously deactivating S2. The water level gradually rises and first closes the S2 electrode (nothing happens - it is disconnected by the contacts K1.1), and then S3. The transistors switch again, the relay picks up and turns off the pump, while simultaneously bringing the S2 sensor into operation for the next cycle.

The device can use any low-power relay that operates from 12 V, the contacts of which are capable of withstanding the pump starter current.

If necessary, the same scheme can be used for automatic pumping of water, say, from the basement. To do this, the drain pump must be connected not to the normally closed, but to the normally open contacts of relay K1. The scheme will not require any other changes.

In one of the articles I saw a variant of the automatic maintenance of the water level in the storage tank proposed by one of the summer residentswhich, to be honest, alarmed me. This design has a number of disadvantages: it is difficult to manufacture, requires a certain level of skill when working with electronic components, and is quite expensive - one transformer is worth it.

But its main drawback is the low level of electrical safety. In the event of a breakdown of the transformer insulation, the mains voltage through the sensor electrodes will enter the water and be transferred to the tank, which can lead to electric shock to people.

I propose in all respects a simple and very cheap version of the automatic water level maintenance scheme (see Fig. 1).

It consists of only one relay and two sensors. As the first component, it is necessary to use a two-position relay K1, and as the second one - reed switches G1 (low water level sensor) and G2 (high water level sensor), located on a guide for a permanent magnet vertically installed outside the tank.

Moreover, the G1 sensor must be located above the G2. The distance between them will correspond to the allowable difference between the upper and lower water levels in the tank. The sensors are triggered by a permanent magnet Q connected to a foam float located inside the tank on its guide. This connection can be done, for example, by using a fishing line through a pulley mounted at the top of the tank.

A sketch of a device for automatically maintaining the water level in the storage tank is shown in Fig. 2. For information about the switched on position of the pump motor, the circuit has an LED indicator HL

The scheme works as follows. In the initial state (there is no water in the tank and, under the influence of the magnet, the reed switch contact G1 is closed), relay K1 must be forced into a state in which its contact K1.2L and contacts K1.3, K1.4 K1.5, K1 connected in parallel will be closed .6, K1.7, K1.8 and K1.9. The pump motor M will start to run and the HL LED will light up to confirm this.

When the tank is filled with water, the float rises and the contact of the G1 sensor opens.

When the tank is filled to the upper level, the magnet moving down the guide acts on the G2 sensor, and then its contact closes. Relay K1 will switch, its contacts K1-2, K1.3, K1LK1.5, K1.6, K1.7, K1L and K1.9 will open, and contact K1.1, on the contrary, will close. And then the pump motor will stop and the HL LED will turn off

When the water level in the tank drops to the lower level, the float drops, and the magnet moving up the guide acts on the G1 sensor and closes its contact. Relay K1 will switch to its original position, its contacts K1.2, K1.3, K1.4, K1.5, K1.6, K1.7, K1.8 and K1.9 will close.

The pump motor will start running again (and the HL LED will light up accordingly). These cycles will repeat as long as voltage is applied to the circuit.

In fact, it took a lot of time to explain how it all works. In fact, the whole device is simpler than a steamed turnip, and since there are no complex nodes in it, then it will work reliably and for a long time. And now about the materials and technical characteristics of the removal components.

As relay K1, I used a relay of the RP-9 type, designed for 220 V AC voltage. You can also put RP-12 (also for 220 V), but with a high power of the pump motor, an intermediate contactor will have to be added to the circuit.
Any reed switches designed for a switching current of at least 100 mA can be used as sensors G1 and G2.
Any indicators are suitable as an HL indicator, for example, LED type SKL12 or AD22-22DS for 220 V.
A piece of plastic cable duct with a rectangular profile of 10 × 15 mm can be used as a guide for the magnet.
As a float, a piece of foam plastic with a rectangular hole 12 × 17 mm in the center.
A piece of plastic cable duct with a rectangular profile 10 × 15 mm can also be used as a guide for the float.
As a magnetic element, you can use a magnet from a magnetic furniture latch, to which a strip of tin with a hole for a fishing line is magnetized and glued.
Sensors (reed switches) can be attached to the rail with ordinary tape.
Fuses FU1 and FU1 of any type for a current of 5 A are used as protection elements.
To de-energize the device circuit, a paired switch with contacts SA1 and SA2 is used.

Scheme of automatic maintenance of water in the storage tank

Fig 1 (top). Schematic diagram of a device for automatically maintaining the water level in the storage tank.
Fig 2. Sketch of the device for automatic maintenance of the water level in the storage tank.

A large water container in your country house or garden plot can be used to water or supply water to your home. When filling it, there is no need to constantly climb up the stairs and monitor the level all day - this may well be done by electronic sensors.

Advanced dachas and farms involved in the cultivation of fruits and vegetables use drip-like irrigation systems in their work. To ensure automatic operation of irrigation equipment, the design requires a large capacity for collecting and storing water. It is usually filled with submersible water pumps in a well, and it is required to monitor the level of water pressure for the pump and its amount in the catchment tank. In this case, it is necessary to control the operation of the pump, that is, to turn it on when a certain level of water in the storage tank reaches and turn it off if the water tank is full. These functions can be realized using float sensors.

Figure: 1 The principle of operation of the float level sensor (RC)

A large storage tank for water may also be required for water supply at home if the flow rate of the water intake tank is very small or the performance of the pump itself cannot provide water consumption corresponding to the required level. In this case, liquid level control devices are also required for the automatic operation of the water supply system.
The liquid level control system can also be used when working with devices that do not have protection against dry running of a borehole pump, a water pressure sensor or a float switch when pumping groundwater from basements and rooms with a level below the earth's surface.

All water level sensors for pump control can be divided into two large groups: contact and non-contact. Non-contact methods are mainly used in industrial production and are divided into optical, magnetic, capacitive, ultrasonic, etc. views. Sensors are installed on the walls of water tanks or directly immersed in monitored liquids, electronic components are placed in a control cabinet.

Figure: 2 Types of level sensors

In everyday life, inexpensive float-type contact devices have found the greatest use, the tracking element of which is made on reed switches. Depending on their location in a container with water, such devices are divided into two groups.

Vertical. In such a device, reed switches are located in a vertical rod, and the float itself with a ring magnet moves along the tube and turns on or off the reed switches.

Horizontal. They are attached to the upper edge on the side of the tank wall, when the tank is filled, the float with a magnet rises on the articulated lever and approaches the reed switch. The device works and switches the electrical circuit placed in the control cabinet, it turns off the power supply to the electric pump.

Figure: 3 Vertical and horizontal reed switches

Reed switch device

The main actuator of a reed switch is a reed switch. The device is a small glass bottle filled with an inert gas or with evacuated air. Gas or vacuum prevents sparks from forming and contact group oxidation. Inside the flask there are closed contacts made of a ferromagnetic alloy of rectangular cross-section (permalloy wire) with gold or silver plating. When it enters the magnetic flux, the contacts of the reed switch are magnetized and repelled from each other - the circuit through which the electric current flows is opened.

Figure: 4 Appearance of reed switches

The most common types of reed switches act on a circuit, that is, when magnetized, their contacts are connected to each other and the electrical circuit is closed. Reed switches can have two leads for closing the opening of the circuit, or three if they work with switching electrical circuits. The low voltage circuit that switches the power supply to the pump is usually housed in a control cabinet.

Wiring diagram for reed switch water level sensor

Reed switches are low-power devices and are not capable of switching large currents, so they cannot be used directly to turn off and on the pump. Usually they are involved in a low-voltage switching circuit for the operation of a powerful pump relay, placed in a control cabinet.

Figure: 5 Wiring diagram for controlling the electric pump using a reed switch float sensor

The figure shows a simple circuit with a sensor that implements control of the drainage pump depending on the water level during pumping, consisting of two reed switches SV1 and SV2.

When the liquid reaches the upper level, the magnet with a float switches on the upper reed switch SV1 and voltage is applied to the P1 relay coil. Its contacts are closed, a parallel connection to the reed switch occurs and the relay is self-locking.

The self-capturing function does not make it possible to turn off the power of the relay coil when the contacts of the enable button are opened (in our case, it is an SV1 reed switch). This happens when the load of the relay and its coil are connected in the same circuit.

The voltage goes to the coil of a powerful relay in the pump power supply circuit, its contacts close and the electric pump starts to work. When the water level falls and the float with the SV2 lower reed switch magnet is reached, it turns on and a positive potential is also supplied to the P1 relay coil on the other side, the current stops flowing and the P1 relay is turned off. This causes a lack of current in the coil of the P2 power relay and, as a consequence, the cessation of the supply voltage to the electric pump.

Figure: 6 Float vertical water level sensors

A similar pump control circuit, placed in a control cabinet, can be used when monitoring the level in a container with a liquid, if the reed switches are reversed, that is, SV2 will be at the top and turn off the pump, and SV1 will turn it on in the depth of the water tank.

Level sensors can be used in everyday life to automate the process when filling large containers with water using electric water pumps. The easiest to install and operate are reed switches manufactured by the industry in the form of vertical floats on rods and horizontal structures.

A self-made device on one transistor can be made by almost anyone who wants it and will make little effort to purchase very inexpensive and not numerous components and solder them into a circuit. It is used for automatic replenishment of water in consumable containers at home, in the country and wherever there is water, without restrictions. And there are a lot of such places. To begin with, consider the diagram of this device. It just couldn't be easier.

Water level control in automatic mode using the simplest electronic water level control circuit.
The entire water level control circuit consists of a few simple parts and if it is assembled from good parts without errors, then it does not need to be configured and will immediately work as planned. A similar scheme has been working for me for almost three years now, and I am very pleased with it.

Automatic water level control circuit

Parts List

The transistor can be applied to any of these: KT815A or B. TIP29A. TIP61A. BD139. BD167. BD815.
ГК1 - lower level reed switch.
ГК2 - top level reed switch.
GK3 - emergency level reed switch.
D1 - any red LED.
R1 is a 3KΩ 0.25 watt resistor.
R2 is a 300 ohm 0.125 watt resistor.
K1 - any 12 volt relay with two pairs of normally open contacts.
K2 - any 12 volt relay with one pair of normally open contacts.
As a signal source for replenishing water in the tank, I used float reed contacts. In the diagram, GK1, GK2 and GK3 are indicated. Made in China, but of very decent quality. I can't say a single bad word. In the container where they stand, I am treating the water with ozone and over the years of working on them, not the slightest damage. Ozone is an extremely aggressive chemical element and it dissolves many plastics completely without any residue.

Now let's consider the operation of the circuit in automatic mode.
When power is applied to the circuit, the float of the lower level of GK1 is triggered and through its contact and resistors R1 and R2 power is supplied to the base of the transistor. The transistor opens and thereby supplies power to the coil of relay K1. The relay turns on and by its contact K1.1 blocks GK1 (lower level), and by contact K1.2 supplies power to the coil of relay K2, which is an executive one and includes an actuator with its contact K2.1. The actuator can be a water pump or an electric valve that supplies water to the container.
The water is replenished and when it exceeds the lower level, the GK1 will turn off, thereby preparing the next cycle of work. Having reached the upper level, the water will raise the float and turn on the GK2 (upper level), thereby closing the chain through R1, K1.1, GK2. The power supply to the base of the transistor will be interrupted, and it will close, turning off the relay K1, which will open K1.1 with its contacts and turn off the relay K2. The relay, in turn, will turn off the actuator. The circuit is prepared for a new cycle of work. GK3 is an emergency level float and serves as an insurance if the upper level float suddenly fails. Diode D1 is an indicator of device operation in water filling mode.
Now let's get down to making this very useful device.

We place the details on the board.

We place all the details on the breadboard so as not to make a printed one. When placing parts, you need to consider to solder as few jumpers as possible. It is necessary to make the most of the conductors of the elements themselves for installation.